Coating device with printhead storage

ABSTRACT

The disclosure concerns a coating device and a corresponding coating process for coating components, in particular motor vehicle body components, with a coating agent (e.g. paint), with a coating robot with a first printhead which is mounted on the coating robot. The disclosure provides that the first printhead is exchangeably mounted on the coating robot and can be exchanged for a second printhead during a color change. Another variant of the disclosure, on the other hand, provides for a second printhead to be mounted on the coating robot in addition to the first printhead, the two printheads each applying a specific coating agent in order to enable a color change without changing the printhead.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of, and claims priority to, U.S. patentapplication Ser. No. 16/468,691, filed on Jun. 12, 2019, whichapplication is a national stage of, and claims priority to, PatentCooperation Treaty Application No. PCT/EP2017/081108, filed on Dec. 1,2017, which application claims priority to German Application No. DE 102016 014 955.8, filed on Dec. 14, 2016, which applications are herebyincorporated herein by reference in their entireties.

BACKGROUND

The disclosure concerns a coating device for coating components with acoating agent, in particular for painting vehicle body components with apaint. Furthermore, the disclosure concerns a corresponding operatingmethod.

For the serial painting of car body components, rotary atomizers areusually used as application devices, which however have the disadvantageof a limited application efficiency, i.e. only a part of the appliedpaint is deposited on the components to be coated, while the rest of theapplied paint must be disposed of as so-called overspray.

A newer development line, on the other hand, provides for so-calledprintheads as application devices, as known for example from DE 10 2013002 412 A1, U.S. Pat. No. 9,108,424 B2 and DE 10 2010 019 612 A1. Incontrast to the known rotary atomizers, such printheads do not emit aspray of the paint to be applied, but a narrowly confined jet of paint,which is almost completely deposited on the component to be painted, sothat almost no overspray occurs.

However, the known printheads are not designed for a color change andare therefore only suitable to a very limited extent for the seriespainting of motor vehicle body components in a paint shop.

In addition, the coating in the printhead can become dry or dry outduring coating breaks, which in the worst case can lead to a loss offunction of the printhead.

Furthermore, regarding the general technical background of thedisclosure, reference is made to DE 601 25 369 T2, DE 10 2010 019 612A1, WO 2005/016556 A1, DE 698 36 128 T2, DE 10 2004 044 655 A1, DE 102013 205 171 A1, DE 600 01 898 T2, EP 1 946 846 A2, DE 10 2013 002 412A1 and DE 689 24 202 T2.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a schematic, highly simplified representation of a coating deviceaccording to the disclosure with a painting robot with a printhead and awet deposit device for deposition of the disassembled printhead,

FIG. 2A is a modification of FIG. 1 , in which a cleaning device isadditionally provided to clean the deposited printhead from the outsideand material circulation through the deposited printhead is possible,

FIG. 2B a flowchart to illustrate a color change process with a storageof the old printhead and a pick-up of a new printhead,

FIG. 3A a modification of FIG. 1 according to the second disclosurevariant with two printheads on the coating robot,

FIG. 3B a highly simplified fluid-technical equivalent circuit diagramof the coating device according to FIG. 3A with an A/B color changer,

FIG. 3C a flow chart to illustrate the A/B operation of the coatingdevice according to FIGS. 3A and 3B,

FIG. 3D a modification of the fluid-technical equivalent circuit diagramaccording to FIG. 3B with two separate color changers for the twoprintheads, and

FIG. 4A-4D various illustrations to explain the various flushingoptions.

DETAILED DESCRIPTION

The disclosure includes two examples, according to which the printheadis replaceably mounted on the coating robot or several printheads aremounted on the coating robot, each of which applies only one specificcoating agent.

The coating device in accordance with the disclosure is preferably usedto paint vehicle body components with a paint and is designedaccordingly.

However, the disclosure also offers the alternative of coating othertypes of components.

Furthermore, the applied coating does not necessarily have to be paint(e.g. water-based paint, solvent-based paint, clear coat, basecoat,etc.). Rather, the disclosure-based coating device can also be designedfor the application of other coating agents, such as adhesives,insulating materials, sealants, primers, etc., to name just a fewexamples.

In accordance with the state of the art, the coating device according tothe disclosure initially has at least one multi-axis coating robot,which preferably has serial robot kinematics, at least six or sevenmovable robot axes and one multi-axis robot hand axis. Such coatingrobots are known from the state of the art and therefore do not need tobe described in detail.

In addition, in accordance with the state of the art, the coating deviceaccording to the disclosure has at least one first printhead to applythe coating agent to the surface of the component to be coated. Theprinthead has at least one nozzle to deliver a coating agent jet of thecoating agent onto the surface of the component to be coated. The term“printhead” used in the disclosure must therefore be distinguished fromthe atomizers usually used as application devices, which do not emit aspatially limited jet of coating agent but a spray of the coating agent.Otherwise, the term “printhead” used in the context of the disclosure isto be understood generally, so that different construction principles ofknown printheads can be used. Preferably, however, the printhead issimilar to the printheads described in DE 10 2013 002 412 A1, U.S. Pat.No. 9,108,424 B2 and DE 10 2010 019 612 A1.

It should also be noted that the printhead has at least one printheadvalve to control the release of coating agent through the nozzle. Forexample, this printhead valve may have an electrically actuated solenoidactuator to adjust the valve position, but the design and operation ofsuch a printhead valve are state of the art and therefore do not need tobe described in more detail

The printhead is mounted on the coating robot and is program-controlledby the coating robot over the surface of the component to be coated,which is also known from the state of the art.

In the first example of the disclosure, the first printhead is mountedon the coating robot and can be exchanged for a second printhead duringa color change, so that the printheads themselves do not have to undergoa color change, but can simply be exchanged by another printhead.

In the second example at least a second printhead is mounted on thecoating robot in addition to the first printhead, whereby the twoprintheads each apply a specific coating agent in order to enable acolor change without changing the printhead. The first printhead canthen apply black paint, for example, while the second printhead canapply silver paint, for example.

In the first example described briefly above, a deposit device ispreferably provided to deposit the first printhead disassembled by thecoating robot in the deposit device and to pick up the second printheadfrom the deposit device instead of the deposited first printhead.

The deposit device is preferably arranged stationary in the coatingdevice and can be reached by the coating robot, so that the coatingrobot can deposit the currently mounted printhead in the deposit deviceand pick up the other printhead previously located in the deposit devicefrom the deposit device. In the case of a color change, the coatingrobot places the mounted printhead in the deposit device and picks up anew printhead from the deposit device so that the new color can then beapplied with this new printhead.

The deposit device may be a wet deposit device or wet holding device inwhich the nozzles of the deposited printhead are kept moist to preventthe liquid coating from drying during storage.

The wet deposit device can also be realized in connection with apermanently mounted printhead, i.e. with a printhead that is notexchangeably mounted on the coating robot. The coating robot can thenplace the printhead in the wet deposit device during coating breaks(e.g. in shift pauses or during maintenance pauses) so that the coatingin the printhead does not dry up.

In an example of such a wet deposit device, a liquid bath can beprovided which is filled with a liquid (e.g. rinsing agent, thinner) andinto which the printhead is at least partially immersed duringdeposition, whereby the liquid prevents the liquid coating agent fromdrying on the outside of the printhead during deposition. When immersingthe printhead in the liquid bath, at least the printhead nozzles shouldbe immersed in the liquid bath, as the nozzles have a very small nozzlecross section and can therefore clog relatively easily.

In another example, the wet deposit device allows fluid circulationthrough the deposited printhead. For this purpose, the printhead has aninlet and an outlet in addition to the nozzles so that a liquid (e.g.coating agent, rinsing agent) can circulate through the printhead. Thewet deposit device then has a docking device that allows docking withcirculation ports to the inlet and outlet of the deposited printhead sothat the Wet Dispenser then circulates a liquid (e.g., coating orrinsing agent) through the deposited printhead. When the printhead isplaced by the coating robot in the wet deposit device, the printhead isseparated from the coating robot and the printhead is connected to thedocking device in the wet deposit device.

The fluid circulation through the deposited printhead can be done withthe previously used paint, so that the printhead is then ready to bepicked up again by the coating robot for application with the samepaint.

Alternatively, it is also possible to clean the deposited printhead witha rinsing agent and then pre-fill (i.e. fill) it with a different paintso that the printhead is ready for application with the new paint.

In the second example at least two printheads are mounted on the coatingrobot, which can be operated alternately. This also enables a so-calledA/B operation, in which printhead A applies coating agent, while theother printhead B is rinsed with a rinsing agent and, if necessary,pre-filled with a different colored coating agent. Then coating agent isapplied with the printhead B, while the printhead A is rinsed withrinsing agent and, if necessary, pre-filled with a coating agent of adifferent color. This A/B operation enables an uninterrupted coatingduring a color change, since you can switch from printhead A toprinthead B or vice versa without a pause. The time required for rinsingand pre-filling the printhead does not interrupt the coating operation.

Furthermore, with the second example it is possible that the at leasttwo printheads on the coating robot can each be supplied with coatingagent by a separate coating agent circuit. In this example and incontrast to the A/B operation described above, no separate A/B valve orcorresponding valve arrangement is required. However, the two coatingcircuits must then be routed through the coating robot to the twoprintheads.

It has already been mentioned briefly above that the second example hasat least two printheads mounted on the coating robot, which can beoperated selectively. Here one coating agent flows through eachprinthead. The number of printheads mounted on the coating robot istherefore preferably greater than 2, and smaller than 6. The individualprintheads are then preferably connected to a separate coating agentsupply line, so that the coating agent supply lines are only passedthrough by the associated coating agent.

With this second example there is also the possibility that someprintheads are intended for frequently used coating agents (“highrunner”) and then only the associated frequently used coating agentflows through them without a color change being provided for theseprintheads. Another part of the printheads or even only one printhead isintended for the application of rarely used coating agents (“lowrunner”) and allows a color change between the different rarely usedcoating agents. This allows the frequently used coating agents to avoidcolor change at all with corresponding losses. When applying the rarelyused coating agents, a color change with corresponding losses isnecessary, but this is of little importance, since the rare coatingagents associated with color change losses are only rarely used.

In addition, the coating device according to the disclosure can have atime control to rinse the printheads time-controlled. For example, thetime control can trigger a rinsing process after a specified rinseinterval, for example after a rinse interval of 1 h, 2 h, or 4 h. Inaddition, there is the possibility that the time control triggers arinsing process after a specified downtime of a conveyor conveying thecomponents to be coated has elapsed, for example after a downtime ofmore than 10 minutes, 20 minutes, 30 minutes or 1 hour. These twovariants of a time control can be used alone or in combination with eachother.

In addition, the coating device according to the disclosure preferablyincludes a cleaning device to clean the mounted or dismountedprintheads. State-of-the-art atomizer cleaning devices are known, intowhich the coating robot introduces the mounted rotary atomizer, wherebythe rotary atomizer is then sprayed inside the cleaning device with acleaning liquid (e.g. thinner) in order to clean the rotary atomizerfrom the outside. The cleaning device according to the disclosure can beconstructed similarly, whereby the cleaning device is naturally adaptedto the different outer contour of the printhead and to missing functionslike e.g. shaping air.

The cleaning device may be located separately from the coating robot,but the cleaning device is located within the working area of thecoating robot so that the coating robot can insert the printhead intothe cleaning device.

In an example of the disclosure, the cleaning device and the depositdevice form a uniform component. This means that the deposit device isnot only used for depositing, picking up and temporarily storing theprintheads, but also for cleaning the printheads in the deposited stateand/or in the mounted state on the coating robot.

The disclosure preferably enables a very short color change time, whichis preferably shorter than 1 h, 20 min, 10 min, 1 min, 30 s, 10 s oreven shorter than 5 s.

In the case of stop-and-go conveying of the motor vehicle bodycomponents through the paint shop, the color change time is preferablyshorter than the change time between two successive motor vehicle bodycomponents, i.e. shorter than the conveying time of the motor vehiclebody components between two positions.

In the case of continuous line tracking conveying of the motor vehiclebody components through the paint shop, however, the color change timeis preferably shorter than the time interval between two successivemotor vehicle body components. In A/B mode, the color change time can beextended to the duration of a car body cycle.

Another advantage is the low loss of coating agent during a colorchange, whereby the loss of coating agent is preferably less than 51,21, 200 ml, 20 ml, 10 ml, 5 ml or even less than 2 ml.

In addition, a color change preferably results in a very low rinsingagent requirement, which is preferably less than 300 ml, 250 ml, 200 ml,100 ml, 50 ml, 20 ml or even less than 10 ml.

In general it should be noted that the printheads preferably emit anarrowly limited jet of coating agent as opposed to a spray mist as isthe case with conventional atomizers (e.g. rotary atomizers).

In a variant of the disclosure, the printheads each emit a droplet jetconsisting of several droplets separated from each other in thelongitudinal direction of the jet, as opposed to a jet of coating agentbeing continuous in the longitudinal direction of the jet.

Alternatively, it is also possible for the printheads to emit acontinuous jet of coating agent in the longitudinal direction of thejet, as opposed to the droplet jet mentioned above.

In the case of the coating device in accordance with the disclosure, thecoating agent pressure is preferably controlled with a very smallfluctuation range, whereby the fluctuation range of the coating agentpressure is preferably smaller than 500 mbar, 200 mbar, 100 mbar or 50mbar.

It should also be mentioned that the printheads preferably have a veryhigh application efficiency of at least 80%, 90%, 95% or 99%, so thatsubstantially all of the applied coating agent is completely depositedon the component without overspray. The printheads are thereforeessentially overspray-free within the scope of the disclosure.

In addition, it should be noted that the printheads preferably have asufficiently high surface coating performance to paint vehicle bodycomponents, for example. The surface coating performance is thereforepreferably at least 0.5 m²/min, 1 m²/min, 2 m²/min or even 3 m²/min.

It should also be noted that the volume flow of the applied coatingagent and thus the exit velocity of the coating agent are preferablyadjusted so that the coating agent does not bounce off the componentwhen it hits it. Furthermore, the impact velocity of the coating agentjet should be designed in such a way that the coating agent does notpenetrate the underlying paint layer, but the coating agent lies on it(layers). The exit velocity of the coating agent is therefore preferablyin the range of 5 m/s to 30 m/s. The coating agent is applied to thesubstrate at a speed of 5 m/s to 30 m/s. The coating agent is thenapplied to the substrate. The application distance is preferably in therange of 4 mm to 200 mm.

Finally, it should be mentioned that the control of the at least oneprinthead valve is preferably done by an electrically controllableactuator, for example by a magnetic actuator or a piezo actuator,whereby such actuators are known from the state of the art and thereforedo not need to be described in detail.

It should also be mentioned that the disclosure does not only claimprotection for the coating device described above. Rather, thedisclosure also claims protection for a corresponding coating process,whereby most of the method steps already result from the abovedescription, so that a separate description of the individual methodsteps can be dispensed with.

In addition, however, it should be mentioned that during a color changefrom a solvent-based paint to a water-based paint, it is preferable tofirst use a solvent-based rinsing agent, then optionally a release agent(e.g. alcohol) and then a water-based rinsing agent. If the change froma water-based to a solvent-based coating is reversed, this sequence mustof course be reversed.

The disclosure also offers the possibility of sequential rinsing withdifferent rinsing agents, for example with an increasing content oforganic solvents.

It is also possible to use a universal rinsing agent for rinsing, whichis used both for rinsing out water-based paint and for rinsing outsolvent-based paint.

In addition, rinsing can be assisted by introducing pulsed air and/or anaerosol of compressed air and rinsing agent into the printhead and/orcleaning device.

It should also be mentioned that the rinsing agent can also be aVOC-free (VOC: Volatile Organic Compound).

In addition, it is advantageous if the residual liquids (e.g. oldcoating agent, rinsing agent residues, etc.) are collected and disposedof during a rinsing process in order to avoid contamination of thecoating device.

The above applies both to flushing the media-carrying areas inside theprinthead or printhead supply lines and to cleaning or flushing theprinthead in the cleaning device.

In addition, it is advantageous if the printhead is pre-filled with thenew coating agent after a rinsing process so that it is immediatelyavailable for application. When this is done, it is preferable tosqueeze a defined amount of the new coating agent out of the printheadnozzles, whereby the squeezed out amount of coating agent is thenpreferably collected and disposed of. In practice, the pressure isprobably applied only before application.

It has already been mentioned above that the printhead valve can becontrolled by a solenoid actuator. Such solenoid actuators usually havean electric coil wound onto a coil tube, with an armature movablyarranged in the coil tube and displaced depending on the current appliedto the coil to close or open the nozzle. Here there is the possibilitythat coating agent can enter the coil tube. The coil tube of themagnetic actuator is therefore also preferably flushed during a rinsingprocess. Here it is possible that the rinsing agent is led through thecoil tube through a separate rinsing connection in the direction of thenozzle. Conversely, it is also possible for the rinsing agent to flow inthe opposite direction through the coil tube, i.e. to a separateflushing outlet. In addition, these two types of flushing can also becombined alternately.

Furthermore, the printhead can be flushed with rinsing agent through thereturn, i.e. the rinsing agent is introduced into the inlet of theprinthead and then enters the return through the outlet of theprinthead, whereby the nozzles are then preferably closed.

In addition, it is also possible for the rinsing agent to be introducedinto the printhead through the inlet and then to exit through thenozzles when the printhead valves are open in order to flush the nozzlechannels.

Furthermore, the disclosure also offers the possibility that the rinsingagent may remain at least partially as a barrier medium in the coil tubeafter a color change in order to prevent coating agent from entering thecoil tube at all.

The second example involves designing the printhead in such a way that acolor change is possible during coating operation. This is achieved bythe fact that the printhead can be rinsed with a rinsing agent during acolor change in order to rinse out coating agent residues from theprinthead.

In accordance with the state of the art, the printhead according to thedisclosure has a coating agent supply in order to supply the coatingagent to be applied to the printhead. In addition, the disclosureprinthead preferably also has a separate rinsing agent supply to supplya rinsing agent. It should be mentioned here that the coating agentsupply is preferably separated from the rinsing agent supply, so thatthe printhead preferably has separate inlets for the supply of thecoating agent on the one hand and for the supply of the rinsing agent onthe other hand.

For a few colors, one color hose (coating agent supply) per color couldbe connected to the applicator (printhead) (Integrated Color Changertechnology). Then there is a rinsing agent connection and a pulse airconnection in or on the applicator. These are then used for rinsing.

In addition, the printhead according to the disclosure alsopreferentially has a recirculation system in order to return coatingagents and/or rinsing agents, either to a ring line or to disposal. Inaddition to the separate connections for the supply of the coating agentand the rinsing agent, the printhead according to the disclosure alsohas a separate connection for returning the coating agent or the rinsingagent.

The recirculation flow to the recirculation is preferably controlled bya controllable recirculation valve, which can be either a self-actuatedrecirculation valve or a proportional valve. Such valve types are knownfrom the state of the art and therefore do not need to be described indetail.

In an example of the disclosure, the printhead has several nozzles fordispensing the coating. A control valve is preferably assigned to eachindividual nozzle in order to control the release of the coating agentthrough the respective nozzle. The above mentioned rinsing agent supplythen may have branch lines leading to the individual control valves sothat all control valves of the pressure head can be flushedsimultaneously with the rinsing agent.

The individual branch lines of the rinsing agent supply are preferablydesigned in such a way that the rinsing agent supplied is distributedevenly over the branch lines to the control valves so that theindividual control valves are flushed essentially with the same amountof rinsing agent.

In an example of the disclosure, the printhead has at least one nozzlefor dispensing the coating agent and an associated control valve forcontrolling the dispensing of the coating agent through the nozzle, asexplained briefly above. The control valve can have an electric coil,which can be wound onto a coil tube, as in the case of the known designdescribed above. It was already explained at the beginning about thestate of the art that coating residues can be deposited in this coiltube, which on the one hand can impair the functionality of the controlvalve and on the other hand can prevent the color change capability. Inthe case of the printhead according to the disclosure, the rinsing agentsupply line therefore preferably flows into the coil tube in order toflush the inside of the coil tube.

It should be mentioned here that the coil tube—as in the conventionalcontrol valve described above—preferably has a circular internalcross-section and contains a coil core. Here it can be advantageous ifthe coil core has a profile cross-section which does not completely fillthe internal cross-section of the coil tube in order to leave space forthe rinsing agent between the coil tube and the coil core so that therinsing agent can flow through in the axial direction. For example, thecoil core may have a star-shaped profile cross-section with radiallyprojecting ribs running in the axial direction, so that the flushingmedium can flow between the ribs of the coil core in the axialdirection.

Alternatively, it is possible for the coil core to have a flushinggroove in its circumferential surface that can run axially, in thecircumferential direction or spirally, for example.

In addition, axial flushing channels can also be arranged in the coilcore.

Another example shows that the profile cross-section of the coil core isgrid-shaped and can be flowed through by the rinsing agent.

It should also be mentioned that the coil core is preferably sealedagainst the coil tube with a seal, in particular with a pressureresistance of more than 2 bar, 4 bar or 6 bar.

It has already been briefly mentioned above that the printhead may haveseveral control valves, all of which can be flushed. The individualcontrol valves usually have one coil tube each, whereby the rinsingagent supply then flows into all coil tubes in order to flush all coiltubes.

It should also be mentioned that the control valve usually has a movablearmature, as in the known control valve described at the beginning,which is moved depending on the current supplied to the coil and closesor releases the nozzle depending on its position.

This armature may run coaxially on part of its length in the coil tubeand preferably has an axially permeable profile cross-section so thatflushing fluid can flow between the armature and the inner wall of thecoil tube. For this purpose, the armature preferably has a non-circularprofile cross-section which does not completely fill the circularinternal cross-section of the coil tube and therefore permits an axialflow of rinsing agent. For example, the profile cross-section of thearmature can be star-shaped or cross-shaped.

In an example, the rinsing agent supply flows axially between thearmature and the coil core into the coil tube.

In another v example the rinsing agent supply opens in the axialdirection in the area of the coil core into the coil tube, in particularat the end of the nozzle tube remote from the movable armature.

In another example, the movable armature is arranged in a guide cagepermeable to flushing medium, in particular in a slotted cylinder. Thisoffers the advantage that the movable armature can be flushed during arinsing process, thus avoiding coating deposits on the armature.

In another v example, the sliding anchor has a central guide hole with aguide pin projecting into the guide hole. This results in a linearguide, which can also be flushed.

In another example, a flexible diaphragm is provided which separates thecontrol valve from the coating agent supply so that the control valve isprotected by the diaphragm against contact with a coating agent. Thismeans that the control valve itself does not have to be flushed at all,as the control valve itself does not come into contact with therespective coating agent at all. Rather, only the smooth surface of thediaphragm on the coating side should be rinsed, which is, however, veryeasy and efficient since the smooth diaphragm surface hardly forms anystarting points for paint deposits.

The printhead according to the disclosure preferably enables a fastcolor change within a color change time of less than 1 h, 20 min, 10min, 30 s, 10 s or even less than 5 s.

The aim is to achieve the lowest possible paint change losses, which arepreferably smaller than 51, 21, 200 ml, 20 ml, 10 ml, 5 ml or evensmaller than 2 ml with the printhead according to the disclosure.

This also leads advantageously to a very lower rinsing agent consumptionwith a color change, whereby the rinsing agent consumption is preferablysmaller than 10 l, 5 l, 2 l, 200 ml, 100 ml, 50 ml, 20 ml or evensmaller than 10 ml.

The disclosure also allows the printhead to be equipped with severalseparate rinsing agent supplies to supply different rinsing agents,which can be adapted to the respective coating agent, for example.

It should also be mentioned that the printhead with its media-carryingparts is preferably designed in such a way that the media-carrying partsare free of dead space and/or undercuts in order to improve rinsability.

To improve rinsability, it is also possible for the printhead to becoated with an easy-to-clean coating on the surfaces that come intocontact with the coating.

Furthermore, it should be noted that the disclosure does not only claimprotection for the printhead according to the disclosure as describedabove as a single component or as a replacement part. Rather, thedisclosure also claims protection for a complete coating device withsuch a printhead.

In addition, the coating device according to the disclosure preferablyalso includes a color changer, such as a linear color changer, a rotarycolor changer, a color changer integrated in the printhead or an A/Bcolor changer. These types of color changers are known from the state ofthe art and therefore do not need to be described further.

Finally, the disclosure also includes a corresponding operating methodfor such a printhead, whereby the individual method steps already resultfrom the above description and therefore do not need to be described inmore detail.

However, it should be mentioned that the rinsing agent can be auniversal rinsing agent that is suitable for both water-based andsolvent-based coatings. In addition, the rinsing agent can be a VOC-free(VOC: volatile organic compounds) rinsing agent.

During the rinsing process, the printhead can also be rinsed togetherwith the rinsing agent or alternately with pulsed air.

It is also possible to supply the printhead with an aerosol for rinsing.

The disclosure also offers the possibility of supplying the printheadwith different rinsing agents one after the other.

In a variant of the operating method according to the disclosure, asolvent-based paint is first supplied and applied. The printhead is thenrinsed with a solvent-based rinsing agent to rinse out residues of thesolvent-based paint. An optional release agent can then be added, suchas alcohol. In the next step, a water-based paint is added and applied.Finally, the printhead is rinsed with a water-based rinsing agent torinse out any residues of the water-based paint.

The above description explains a change from a solvent-based coating toa water-based coating. Of course, it is also possible to switch from awater-based to a solvent-based coating, which requires a correspondingchange in the sequence of the method steps described above.

After a color change, the printhead is preferably pre-filled with thenew coating, i.e. filled. A defined amount of coating is preferablyapplied through the nozzle of the printhead.

When operating the printhead according to the disclosure, it is alsopossible that all fluids (coating agent and rinsing agent) releasedduring a rinsing process are collected for disposal.

It is also possible for the outer surface of the nozzle head to berinsed during the color change in order to remove any coating agentresidues adhering to it.

It should also be mentioned that the rinsing agent can be discharged oneafter the other or alternately into the recirculation system or throughthe nozzle. In addition, there is also the option of rinsing with amixture of rinsing agent and pulsed air.

FIG. 1 shows a very simplified, schematic representation of an paintinginstallation according to the disclosure for painting vehicle bodycomponents 1, which are conveyed by a conveyor 2 at right angles to thedrawing plane along a painting line through the painting installation,whereby the conveying can take place either in stop-and-go operation orin line tracking operation, which is known per se from the state of theart and therefore does not need to be described in more detail.

Next to the conveyor 2, a painting robot 3 is simplified, whereby thepainting robot 3 has a robot base 4, a rotatable robot member 5, aproximal robot arm 6 (“arm 1”), a distal robot arm 7 (“arm 2”) and amulti-axis robot hand axis 8, which is known from the state of the art.The robot base 4 can either be fixed here or moved along anunrepresented traversing rail at right angles to the drawing plane.

The rotatable robot member 5 can be rotated about a vertical axis ofrotation relative to the robot base 4.

The proximal robot arm 6, on the other hand, can be swivelled about ahorizontal swivel axis relative to the rotatable robot member 5.

The distal robot arm 7 can also be swivelled about a horizontal swivelaxis relative to the proximal robot arm 6.

The robot hand axis 8 has a mounting flange on which a printhead 9 ismounted. The printhead 9 has a large number of nozzles to emit a jet ofcoating agent onto the surface of the motor vehicle body part 1.

In addition, the coating device shown has a wet deposit device 10 whichis filled with a liquid bath 11, whereby the liquid may, for example, bea thinner. The liquid bath 11 may also contain a soaked pad or sponge asan alternative to moistening printhead 9.

During a color change, the coating robot 3 places the printhead 9 in theliquid bath 11 and takes another printhead from the wet deposit device10, so that another paint can then be applied with the new printhead(not shown).

In addition, the coating robot 3 positions the printhead 9 in the liquidbath 11 during longer coating pauses to prevent the coating from dryingin the nozzles of the printhead 9.

It should be mentioned that the drawing only shows a simplifiedschematic representation of this example.

FIG. 2A shows a modification of the example according to FIG. 1 , sothat in order to avoid repetitions, reference is made to the abovedescription, whereby the same reference signs are used for thecorresponding details.

A feature of this example is that the wet deposit device 10 is alsodesigned as a cleaning device and contains cleaning nozzles 12 forspraying the deposited printhead 13 from the outside with a cleaningliquid (e.g. thinner).

Another feature of this example is that the wet deposit device 10contains a docking device 14 which can establish a flow connection withthe deposited printhead 13. Thus the printhead 13 has an inlet in orderto be able to introduce liquid (e.g. paint, rinsing agent) into theprinthead 13. In addition, the printhead 13 has an outlet fordischarging the liquid (e.g. paint, rinsing agent) from the printhead13. The docking device 14 can now dock to the inlet and outlet of thedeposited printhead 13 so that fluid can circulate through the depositedprinthead 13 via circulation lines 15, 16.

For example, the same paint that was previously applied by the printhead13 can then flow through the deposited printhead 13 via the circulationlines 15, 16.

Alternatively, it is possible to carry out a color change using thedocking device 14. In this case, the deposited printhead 13 is firstrinsed with a rinsing agent via the circulation lines 15, 16 in order toclean the printhead 13. Then the deposited printhead 13 can bepre-filled with the new paint, so that the printhead 13 is immediatelyavailable for application with the new paint.

FIG. 2B shows the operating mode of the coating device according to FIG.2A in a flowchart.

In a step S1, the coating is first carried out with a printhead A, whichis mounted on the painting robot 3.

If it is determined in a step S2 that a color change is required, themounted printhead A is then first deposited in a step S3 in the wetdeposit device 10.

In a step S4, a printhead B from the wet deposit device 10 is thenpicked up by the painting robot 3.

The deposited printhead A is then cleaned in a step S5 in the wetdeposit device 10 and rinsed in one step S6.

In step S7, the deposited printhead A is then pre-filled with a newpaint.

Meanwhile, in a step S8, the new printhead B can already be coated withthe new paint.

FIGS. 3A-3C are used to explain a variation of the example in FIGS. 2Aand 2B so that to avoid repetition, reference is made to the abovedescription, using the same reference signs for corresponding details.

A feature of this embodiment is that two printheads A, B are mounted onthe painting robot 3, which enables a so-called A/B operation by meansof an A/B color changer 17. The A/B color changer 17 is connected viatwo parallel color lines 18, 19 to the two printheads A, B, which canreturn the unneeded paint or rinsing agent residue to a return line RAor RB respectively.

FIG. 3C shows the function of the so-called A/B operation with thecoating device according to FIGS. 3A and 3B.

In a first step S1, it is initially painted with the printhead A.

If it is then determined in step S2 that a color change is to takeplace, step S3 switches over to the other printhead B.

Then, in step S4, printhead A is rinsed and then pre-filled in step S5with the desired new paint.

At the same time, a new coating can be applied without interruption withprinthead B in step S6. Steps S4 and S5 therefore do not delay the colorchange, so that the coating can be applied almost without interruptionduring a color change.

If in step S7 it is then determined again that a new color change is totake place, then in step S8 it is switched to the printhead A again andthe printhead B is rinsed at step S9 and pre-filled in step S10 with anew paint.

FIG. 3D shows a modification of the fluid equivalent schematic as shownin FIG. 3B, so that to avoid repetitions, reference is made to the abovedescription, using the same reference signs for corresponding details.

A feature of this embodiment is that two separate color changers 17.1,17.2 are provided instead of the A/B color changer 17.

FIGS. 4A-4D show a schematic diagram of a printhead with multipleprinthead valves 20 to control coating delivery. The shown printhead hasa nozzle plate 21 with numerous nozzles 22 which can be closed or openedby the individual printhead valves 20.

The individual printhead valves 20 are electrically controlled andoperate magnetically. The printhead valves 20 each have a coil 23 woundonto a coil tube 24, the coil tube 24 having a coil core 25 and amovable armature 26. The armature 26 can be moved vertically in thedrawing and is pressed by a return spring 27 into the closed positionshown in the drawings, in which a seal 28 at the lower end of thearmature 26 closes the nozzle 22.

To open the printhead valve 20, the coil 23 is energized in such a waythat the armature 26 is pushed upwards in the drawing, so that the seal28 releases the nozzle 22.

In addition, the individual printhead valves 20 each have a rinse ports29 at the top end.

The printhead itself has an inlet 30 for supplying paint or rinsingagent and an outlet 31 for dispensing paint or rinsing agent.

As for the drawings in FIGS. 4A-4D, it should be noted that in thedrawings all printhead valves 20 are shown in the closed state and thenozzles 22 then close. In fact, however, the individual printhead valves20 must open or close in order to perform the rinsing operationsdescribed below.

It should also be mentioned that the drawings show the flow path of therinsing agent in the various rinsing processes by means of a largearrow.

In FIG. 4A, the flushing fluid is introduced into the printhead throughthe inlet 30 and then leaves the printhead through the outlet 31 intothe return, with all printhead valves 20 being closed.

In the flushing procedure shown in FIG. 4B, the flushing fluid is alsofed into the printhead through the inlet 30 and then leaves theprinthead through the nozzles 22. In this flushing procedure, theindividual printhead valves 20 are opened which is different from thedrawing.

In the rinse operation shown in FIG. 4C, however, the rinsing agent isfed through rinse ports 29 of each printhead valve 20 and then leavesthe printhead through nozzles 22. Again, each printhead valve 20 releasenozzle 22 differently from the drawing.

In the flushing procedure shown in FIG. 4D, however, the rinsing agentis introduced in the reverse direction through the open nozzles 22 andthen leaves the printhead via the rinse ports 29 of the individualprinthead valves 20 and/or (not shown) via the return. Thus, within thescope of the disclosure, there is the possibility that the coil tubes 24of the individual printhead valves 20 can be flowed throughbidirectionally by flushing medium in order to achieve a good flushingeffect.

The disclosure is not limited to the preferred embodiments describedabove. Rather, a large number of variants and modifications are possiblewhich also make use of the disclosure and therefore fall within thescope of protection. In particular, the disclosure also claimsprotection for the subject-matter and the features of the dependentclaims independently of the claims referred to in each case and inparticular also without the features of the main claim. The disclosurethus comprises a large number of different aspects which enjoyprotection independently of each other.

List of reference signs: 1 Motor vehicle body component 2 Conveyors 3Painting robots 4 Robot base 5 Rotatable robot link 6 Proximal robot arm(″Arm 1″) 7 Distal robot arm (″Arm 2″) 8 Robot hand axis 9 Printhead 10Wet deposit device 11 Liquid bath 12 Cleaning nozzles in the wet depositdevice 13 Deposited printhead in the wet deposit device 14 Dockingdevice in the wet deposit device 15 Circulation line in the wet depositdevice 16 Circulation line in the wet deposit device 17 A/B colorchanger 17.1 Color changer 17.2 Color changer 18 Color lines 19 Colorlines 20 Printhead valves 21 Nozzle plate 22 Nozzles 23 Coil 24 Coiltube 25 Coil core 26 Armature 27 Return spring 28 Seal 29 Rinse ports 30Printhead inlet 31 Printhead outlet A, B Printheads F1-F6 Color lines PLPulse air line V Thinner line RA, RB Return lines

The invention claimed is:
 1. Coating device for coating components witha coating agent, comprising: a) a multi-axis coating robot, b) a firstprinthead with b1) at least one nozzle for delivering a coating agentjet of the coating agent from the nozzle onto the surface of thecomponent to be coated, and b2) at least one printhead valve forcontrolling the release of the coating agent through the nozzle, b3)wherein the first printhead is mounted on the coating robot and isguided by the coating robot over the surface of the component to becoated, c) wherein the first printhead is replaceably mounted on thecoating robot and is exchangeable for a second printhead in the event ofa color change, d) a deposit device for depositing the first printheaddismantled from the coating robot in the deposit device and for takingthe second printhead located in the deposit device instead of thedeposited first printhead for subsequent coating agent application withthe taken second printhead, d1) the deposit device is a wet depositdevice in which the nozzles of the deposited printhead are kept moist inorder to prevent the liquid coating agent from drying during deposition,and d2) the deposit device includes a soaked pad or sponge to moistenthe first printhead in the deposit device.
 2. Coating device accordingto claim 1, wherein the wet deposit device has a liquid bath which isfilled with a liquid and into which the printhead is at least partiallyimmersed during deposition, the liquid preventing the liquid coatingagent from drying during deposition.
 3. Coating device according toclaim 1, wherein said wet deposit device has circulation lines forcirculating said coating agent or a rinsing agent through said depositedprinthead during deposition.
 4. Coating device according to claim 1,wherein a) a separate printhead is each attached to the coating robotfor each coating agent to be applied, so that the printheads are eachonly flowed through by the associated coating agent, and b) the numberof printheads mounted on the coating robot is greater than 2, and c) thenumber of printheads mounted on the coating robot is smaller than 6, andd) the individual printheads are each connected to a separate coatingagent supply line, so that only the associated coating agent flowsthrough the coating agent supply lines in each case.
 5. Coating devicein accordance with claim 1, wherein a) a separate printhead is alwayspresent in the deposit device for each coating agent to be applied, sothat only the associated coating agent flows through the printheads ineach case, and/or b) the number of printheads mounted on the coatingrobot is greater than 2 and less than 50 and c) the individualprintheads are each connected to a separate coating agent supply line,so that only the associated coating agent flows through the coatingagent supply lines in each case.
 6. Coating device according to claim 1,further comprising a time control for time-controlled flushing of atleast one of the first printhead and the second printhead with a rinsingagent.
 7. Coating device according to claim 6, wherein the time controltriggers a rinsing operation of at least one of the first printhead andthe second printhead after a predetermined rinsing interval has expired.8. Coating device according to claim 6, wherein the time controltriggers a rinsing process of at least one of the first printhead andthe second printhead after a predetermined standstill period of aconveyor conveying the components to be coated has elapsed.
 9. Coatingdevice according to claim 3, wherein the circulation lines include thecoating agent therein.